Samples of ambient aquarium water (inhalant) and oscular stream (exhalant) of the sponges Haliclona permollis (Bowerbank) and Suberites ficus (Johnston) were analyzed for bacteria by three methods. Bacterial removal efficiencies were 70.3 and 77% from plate cultures, 44 and 68% from surface fouling, and 77% from direct filter counting in a single transit of the sponge filter. Bacteria alone can satisfy the entire food requirements for these sponges. Bactericidal activity is not expressed in exhalant water samples. If bacterial toxins are produced by these sponges, their activity must be restricted to local sites within the confines of the organisms.